1. Field of the Invention
The present invention relates to a system for controlling a change of channel data sequence order for a PCM terminal device and, more particularly, to a sequence order control system which allows easy discrimination of channel data in a PCM terminal device having a number of channels.
2. Description of the Related Art
A conventional PCM terminal device comprises a plurality of channel boards each having transmitting and receiving portions, a multiplexing portion, a demultiplexing portion, a sequence order signal generator, a transmitting side channel pulse conversion portion, and a receiving side channel pulse conversion portion. The multiplexing portion transmits as PCM transmission data a frame constituted of 8-bit time slots TS1, TS2, . . . , TS24 following 1-bit frame identification data. The time slots TS1, TS2, . . . , TS24 of this data format correspond to transmission data sequentially transmitted from a transmitting portion in each channel board. In the conventional PCM primary group terminal device, each channel board is connected to a subscriber's telephone, exchange, and other devices.
When the transmitting portion of each channel board receives a transmission pulse from the transmitting side channel pulse conversion portion, it transmits transmission data corresponding to one time slot (8 bits). In this case, the time slots storing channel data of the respective channel boards have a predetermined fixed order, and data is transmitted from the multiplexing portion in this order.
In PCM reception data, the position of each time slot for each channel in the frame is fixed. Therefore, the demultiplexing portion transmits the time slot following the 1-bit identification data in the predetermined order of the channel boards.
The multiplexing portion multiplexes data transmitted from the channel boards as PCM transmission data in the predetermined order. Thus, the transmitting side channel pulse converter transmits the channel pulse P1 to the corresponding channel board transmitting portion to cause it to generate 8-bit transmission data, and then transmits the channel pulse P2 to the corresponding transmitting portion to cause it to generate 8-bit transmission data. In this way, when channel pulses P1, P2, . . . , P24 are sequentially transmitted to the transmitting portions of the channel boards, 8-bit transmission data is sequentially supplied to the multiplexing portion. Thus, the multiplexing portion generates the frame consisting of the time slots following the 1-bit identification bit. This control is repeated, and PCM transmission data is transmitted.
The demultiplexing portion processes PCM reception data in a manner opposite to that of the PCM transmission data. Since the order of time slots including the channel data in the frame is fixed, the channel pulses P1, P2, . . . are transmitted to the channel boards corresponding to the above order, and each time slot can be distributed to the receiving portion of the corresponding channel board.
The sequence order signal generator generates an order signal for generating the pulses P1, P2, . . . at predetermined time intervals in response to instructions from the multiplexing and demultiplexing portions. Upon reception of the order signal, the transmitting and receiving side channel pulse conversion portions sequentially transmit the channel pulses.
There is a strong demand for modifying the PCM terminal device by software without modifying the hardware when an office is moved. However, in the conventional PCM terminal device, since the order of channel data and time slots in the frame is predetermined, it is difficult to respond to this demand.
Furthermore, there is a demand for monitoring the operating state of each channel board by checking a specific time slot. However, only an output signal of a specific channel is present in the specific time slot. For example, when time slots are used for monitoring the operating state, since each time slot includes only the output from a certain channel board, the output state of other channel boards cannot be checked. Hence, when monitoring operation is performed using a specific time slot, the outputs of other channel boards must be allocated in the time slot. When this time slot is at a first position, an output of a channel board is inserted therein, and when at a second position, an output of another channel board is to be inserted. In this way, data of the channel boards must be exchanged. However, such an operation is complex, resulting in inconvenience.
Therefore, the present invention intends to solve the above drawbacks with a simple method.